<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body {
            background-color: gray;
        }
    </style>
</head>
<body>

<!--
    9.CSS背景
      1)background-color:背景色(transparent/color)
      2)background-image:背景图(none/ur1)
      3)background-repeat:背景图像铺排方式(repeat/no-repeat/repeat-x/repeat-y)
      4)background-position:设置对象的背景图像位置({x-number|top|center|bottom}{y-number|left|center|right})
      5)background-attachment:背景图像滚动位置(scroll/fixed)
      6)background 背景的复合写法
        background: color image repeat attachment position
-->
<p></p>


</body>
</html>